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linux-sg2042/arch/arm/include/asm/highmem.h

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[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H
#include <asm/kmap_types.h>
#define PKMAP_BASE (PAGE_OFFSET - PMD_SIZE)
#define LAST_PKMAP PTRS_PER_PTE
#define LAST_PKMAP_MASK (LAST_PKMAP - 1)
#define PKMAP_NR(virt) (((virt) - PKMAP_BASE) >> PAGE_SHIFT)
#define PKMAP_ADDR(nr) (PKMAP_BASE + ((nr) << PAGE_SHIFT))
#define kmap_prot PAGE_KERNEL
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-30 04:46:02 +08:00
#define flush_cache_kmaps() \
do { \
if (cache_is_vivt()) \
flush_cache_all(); \
} while (0)
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
extern pte_t *pkmap_page_table;
[ARM] introduce dma_cache_maint_page() This is a helper to be used by the DMA mapping API to handle cache maintenance for memory identified by a page structure instead of a virtual address. Those pages may or may not be highmem pages, and when they're highmem pages, they may or may not be virtually mapped. When they're not mapped then there is no L1 cache to worry about. But even in that case the L2 cache must be processed since unmapped highmem pages can still be L2 cached. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-03-13 10:52:09 +08:00
#define ARCH_NEEDS_KMAP_HIGH_GET
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
extern void *kmap_high(struct page *page);
[ARM] introduce dma_cache_maint_page() This is a helper to be used by the DMA mapping API to handle cache maintenance for memory identified by a page structure instead of a virtual address. Those pages may or may not be highmem pages, and when they're highmem pages, they may or may not be virtually mapped. When they're not mapped then there is no L1 cache to worry about. But even in that case the L2 cache must be processed since unmapped highmem pages can still be L2 cached. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-03-13 10:52:09 +08:00
extern void *kmap_high_get(struct page *page);
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
extern void kunmap_high(struct page *page);
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-30 04:46:02 +08:00
extern void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte);
extern void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte);
/*
* The following functions are already defined by <linux/highmem.h>
* when CONFIG_HIGHMEM is not set.
*/
#ifdef CONFIG_HIGHMEM
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
extern void *kmap(struct page *page);
extern void kunmap(struct page *page);
extern void *kmap_atomic(struct page *page, enum km_type type);
kmap_atomic: make kunmap_atomic() harder to misuse kunmap_atomic() is currently at level -4 on Rusty's "Hard To Misuse" list[1] ("Follow common convention and you'll get it wrong"), except in some architectures when CONFIG_DEBUG_HIGHMEM is set[2][3]. kunmap() takes a pointer to a struct page; kunmap_atomic(), however, takes takes a pointer to within the page itself. This seems to once in a while trip people up (the convention they are following is the one from kunmap()). Make it much harder to misuse, by moving it to level 9 on Rusty's list[4] ("The compiler/linker won't let you get it wrong"). This is done by refusing to build if the type of its first argument is a pointer to a struct page. The real kunmap_atomic() is renamed to kunmap_atomic_notypecheck() (which is what you would call in case for some strange reason calling it with a pointer to a struct page is not incorrect in your code). The previous version of this patch was compile tested on x86-64. [1] http://ozlabs.org/~rusty/index.cgi/tech/2008-04-01.html [2] In these cases, it is at level 5, "Do it right or it will always break at runtime." [3] At least mips and powerpc look very similar, and sparc also seems to share a common ancestor with both; there seems to be quite some degree of copy-and-paste coding here. The include/asm/highmem.h file for these three archs mention x86 CPUs at its top. [4] http://ozlabs.org/~rusty/index.cgi/tech/2008-03-30.html [5] As an aside, could someone tell me why mn10300 uses unsigned long as the first parameter of kunmap_atomic() instead of void *? Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net> Cc: Russell King <linux@arm.linux.org.uk> (arch/arm) Cc: Ralf Baechle <ralf@linux-mips.org> (arch/mips) Cc: David Howells <dhowells@redhat.com> (arch/frv, arch/mn10300) Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com> (arch/mn10300) Cc: Kyle McMartin <kyle@mcmartin.ca> (arch/parisc) Cc: Helge Deller <deller@gmx.de> (arch/parisc) Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> (arch/parisc) Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> (arch/powerpc) Cc: Paul Mackerras <paulus@samba.org> (arch/powerpc) Cc: "David S. Miller" <davem@davemloft.net> (arch/sparc) Cc: Thomas Gleixner <tglx@linutronix.de> (arch/x86) Cc: Ingo Molnar <mingo@redhat.com> (arch/x86) Cc: "H. Peter Anvin" <hpa@zytor.com> (arch/x86) Cc: Arnd Bergmann <arnd@arndb.de> (include/asm-generic) Cc: Rusty Russell <rusty@rustcorp.com.au> ("Hard To Misuse" list) Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-08-10 08:18:32 +08:00
extern void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
extern void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
extern struct page *kmap_atomic_to_page(const void *ptr);
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-30 04:46:02 +08:00
#endif
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-16 04:44:55 +08:00
#endif